Page 221 - The Miracle of the Blood and Heart

Blood Vessels: A Flawless
Transportation Network

leaking into the tissues. Since there is no more than a very
small amount of leakage of fluid and proteins into the tissues,
no situation arises that might damage the exact balance in the
body. 110
Fat-soluble substances, on the other hand, need not pass
through the capillary gates. They can directly diffuse across the
capillary membrane. This is most important, because this facil-
itated passage permits oxygen and carbon dioxide to be trans-
mitted rapidly and in large quantities. Therefore, these gasses
are transported at a speed several times greater than sub-
stances such as sodium and glucose, which are not liquid-sol-
uble. This is in direct proportion to the tissues' needs for these
gasses, which can pass the gates only when the need arises.

Tissue cells
Capillary's arterial Osmotic Osmotic Capillary's
end pressure pressure venous end

Blood Blood
pressure pressure

Interstitial
fluid Net pressure Net pressure
out in

c) Flow of fluid across the capillary walls generally depend on the difference
between blood pressure and osmotic pressure at different points of the cap-
illary bed. Blood pressure establishes an outward force. Osmotic pressure,
on the other hand, draws the fluid back. As a result, fluid is expelled
from the capillary by means of clefts at the arterial end, and is taken
in the blood again in the venous end.
Adnan
Oktar

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